Macroseismic Constraints on Deep Crustal Structures in the Bohemian Massif

Hrubcová, Pavla; Machek, Matěj; Vackář, Jiří; Pohořalá, Anna; Kampfová Exnerová, Hana; Špaček, Petr; Zedník, Jan

doi:10.5194/egusphere-2026-686

Preprints

https://doi.org/10.5194/egusphere-2026-686

Preprints

12 Feb 2026

| 12 Feb 2026

Macroseismic Constraints on Deep Crustal Structures in the Bohemian Massif

Pavla Hrubcová, Matěj Machek, Jiří Vackář, Anna Pohořalá, Hana Kampfová Exnerová, Petr Špaček, and Jan Zedník

Abstract. We analysed two moderate earthquakes that occurred near Mirotice in southern Bohemian Massif (Czechia) in March 2024 (M_L 3.5) and April 2025 (M_L 3.1), integrating seismological analyses with crowdsourced macroseismic observations. Both events originated at unusually large focal depths for the region (23–24 km) and were widely felt across southern and central Bohemia, attracting significant public and scientific attention. Macroseismic effects were documented through extensive citizen participation, with over 1,500 questionnaires for each event collected by the Institute of Geophysics of Czech Academy of Sciences. Maximum macroseismic intensities reached IV–V; however, the spatial distribution of observations was distinctly non–circular, forming a pattern controlled by major tectonic structures. Areas underlain by granitoids of the Central Bohemian Pluton exhibited dense and far reaching macroseismic responses, consistent with low seismic energy attenuation of the Moldanubian, whereas regions dominated by early Palaeozoic sedimentary rocks of the Teplá–Barrandian showed sparse observations, indicating higher attenuation. Focal mechanisms indicated normal faulting on a NW–SE striking fault plane, consistent with regional stress field. The unusually large focal depths may be attributed to low geothermal gradient in the area suggesting deep seated structural controls on earthquake nucleation. The results delineate two subvertical structures within the Bohemian Massif and demonstrate that crowdsourced macroseismic data provide valuable constraints on earthquake effects and deep geological controls on seismic wave propagation, even in regions with low seismicity, and effectively complement instrumental observations.

Received: 04 Feb 2026 – Discussion started: 12 Feb 2026

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19 Aug 2026

Public response to two rare earthquakes: crowdsourcing constraints on crustal structure in south Bohemian Massif

Pavla Hrubcová, Matěj Machek, Jiří Vackář, Anna Pohořalá, Hana Kampfová Exnerová, Petr Špaček, and Jan Zedník

Solid Earth, 17, 979–989, https://doi.org/10.5194/se-17-979-2026,https://doi.org/10.5194/se-17-979-2026, 2026

Short summary

Pavla Hrubcová, Matěj Machek, Jiří Vackář, Anna Pohořalá, Hana Kampfová Exnerová, Petr Špaček, and Jan Zedník

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2026-686', Anonymous Referee #1, 07 Apr 2026
General Comments
The paper aims to investigate deep crustal structures in the Bohemian Massif by integrating seismological data with crowdsourced macroseismic observations. While the manuscript is well-written and provides a thorough geological background of the study area, there is a significant disconnect between the stated objectives and the actual data analysis presented.
The authors claim that the study demonstrates how citizen-reported data can reveal geological controls on earthquake effects. However, the manuscript lacks the analytical support necessary to justify such conclusions. Furthermore, there is a notable absence of macroseismic literature or citations linking macroseismic intensity to geological structures, despite the extensive geological references. In its current form, the paper describes the dataset and the geological setting but falls short of providing the seismological and macroseismic analysis promised in the abstract. Major revisions are required to substantiate the interpretations with quantitative evidence.
Specific Comments
Although the abstract mentions the integration of seismological and macroseismic analyses, no actual seismological analysis is presented; the authors only provide a figure showing waveforms from some stations.

The authors state that individual responses were converted to macroseismic intensities but do not explain the methodology. It is unclear how intensities were calculated, what weights were given to specific answers, or whether intensity was assigned to individual questionnaires or geographic localities.

For low intensities (2–5) such as those discussed here, "not felt" reports are critical. The authors should clarify if they have access to these data and how they were utilized.

Figures 3a and 3c show the locations of observations but fail to display the actual intensity values. Additionally, while Figure 3d shows an area of intensity 2, there is no explanation of how this specific intensity was assigned.

In the Discussion the authors interpret the low density of observations in specific sectors (e.g., NW of the epicenter and near the RBFS structure to the east) as evidence of geological control or seismic energy attenuation. However, a low density of data points may simply reflect low population density or a lack of participation, which provides no objective evidence regarding the actual intensity value. Moreover, in Figure 4 the lack of observations NW of the epicenter appears to coincide with low-density areas. To support these claims, the authors should show the density of observations relative to the population and provide attenuation plots of the intensity values for those specific sectors.

At line 143, it is claimed that a booming sound often preceded the shaking. However, the attached questionnaire does not include a question regarding the timing of the sound; the authors must explain the source of this information. It would also be beneficial to provide a map showing the spatial distribution of these acoustic reports.

At line 247, the macroseismic fields are compared to a field with quadrupolar symmetry, but no bibliographic references are provided to support the existence of such a field.

The manuscript does not specify how the population was invited to complete the questionnaires, which is a vital part of assessing crowdsourced data quality.

Technical Corrections
The citation "Cifelli et al., 1999" (line 54) is missing from the References section.

The Appendix, which defines magnitude and macroseismic intensity, is unnecessary for a specialized scientific journal like Solid Earth and should be removed.

The authors should provide access to the dataset in a dedicated "Data Availability" section.
Citation: https://doi.org/10.5194/egusphere-2026-686-RC1
- AC1: 'Reply on RC1', Pavla Hrubcová, 17 May 2026
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-686/egusphere-2026-686-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2026-686-AC1
RC2:
'Comment on egusphere-2026-686', Anonymous Referee #2, 13 Apr 2026

The paper by Hrubcova and coauthors aims to constrain source characteristics, and deep propagation properties by using online macroseismic questionnaires collected after two recent earthquakes.

Despite the efforts are appreciable, there are many questionable points in the actual release, for which I suggest a major revision, or resubmission. They are listed below.

Major points:

1) About the Tectonic and structural context (lines 56-68, 171-202), text and figures are poorly informative of the actual expected tectonic seismicity: I suggest shrinking the description of the large scale-long time evolution of the orogenic belt in favour of a more detailed qualification of the present seismicity (actually lines 70-76): fig 1 is not sufficiently readable, consider to combine the geological panel with a physical map showing main events from CZEQ catalogue, station locations (e.g. moving the inset of Fig.2) showing for example the country's border, as common reference line.

2) About the selected earthquakes (lines 95-128), no reference is given for the solutions proposed, no details are provided about the location method, accuracy of the solutions and depth control with such a limited station coverage in the surroundings of the epicenter. Searching on ISC bullettins, the solutions provided in the manuscript nearly coincides with the ones given by national agency IPEC The Institute of Physics of the Earth; quite a lot of mining events are listed by ISC, close in space (epicenters) and time to the two mentioned tectonic events: if true, they deserve to be mentioned; a table of the identified aftershock is more informative than the actual Tab 1 (that anyway has to be mentioned in the block of focal mechanism description -lines 122-128). Consider to add a cross-correlation graph/ waveform comparison of the two events at the same station in the inset of Fig 2, to support they are co-located and with the same source mechanism. Some considerations concerning the theoretical radiation pattern of S-waves have to be added too.

3) last but the most important: I find critical and not properly presented the criteria used to assign the macroseismic degree from the questionnaires (basically described only at line 148-154). The literature in Europe on this subject is wide, but basically not quoted. Considering the formulation of questions provided in English in the Annex questionnaire, I believe the indicators of the "strength" of the shakings are still vague (for example the "observer's feelings and reactions" do not include the doubt/surprise, no fear or reaction that is usually associated with degrees II-III), and the final assignment of degrees III, IV and IV-V may overestimates the intensity. A better representation of the population density and description of the engagement of population for the compilation of questionnaires is welcome.

Minor points:

a) magnitude 3.1-3.5 cannot be defined as moderate earthquakes (usually 4.0-5.5), but light ones

b) line 54, Cifelli et al not in reference list

c) line 73 and 389 CZEQ catalogue reference lacks the date

d) references starting at lines 331, 365, 386 and 393 are not cited in the text

e) mistype at lines 407-409

f) wrong date? at reference starting at line 422, in the text quoted without a,b

Citation: https://doi.org/10.5194/egusphere-2026-686-RC2
- AC2: 'Reply on RC2', Pavla Hrubcová, 17 May 2026
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-686/egusphere-2026-686-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2026-686-AC2

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

AR by Pavla Hrubcová on behalf of the Authors (17 May 2026) Author's tracked changes Manuscript

EF by Mario Ebel (18 May 2026) Author's response

ED: Referee Nomination & Report Request started (20 May 2026) by Simone Pilia

RR by Anonymous Referee #1 (29 May 2026)

Suggestions for revision or reasons for rejection

General comments
The authors have submitted a second version of the manuscript, introducing several revisions that have improved various aspects of the paper. However, despite these changes, some fundamental issues remain unresolved and the manuscript still does not meet the standards required for publication in Solid Earth. In particular, the statement conveyed by the title, “Crowdsourcing Constraints on Crustal Structure in South Bohemian Massif”, is not supported by any quantitative analysis. Instead, it relies only on a visual comparison between the locations of volunteered observations and some tectonic lineaments. Such an approach is insufficient to support the main conclusion reported in lines 315–316: “The results demonstrate that major crustal-scale tectonic boundaries strongly influence seismic wave propagation and attenuation.”
Specific comments
In lines 156–166, the authors state that “Intensities were initially assigned to individual reports and subsequently evaluated for localities”. However, Figure 3 shows individual intensities and an interpolated field, while intensity data aggregated by locality are not shown. Furthermore, the manuscript does not explain how the interpolated field was obtained, nor whether it was derived from individual reports or from locality-based intensity values.
In line 175, the authors add, without any supporting references, that “the not-felt reports were associated with the perception of sounds resembling transport heavy vehicles”. However, this procedure is problematic, since this is one of the typical noises historically described in association with earthquake shaking, already by Davison (1938). The procedure may be reasonable only if no shaking-related effects, other than the acoustic effect, were reported. If this is the case, it should be explicitly stated. Moreover, the rationale for assigning intensity 3 to these claimed not-felt reports remains unclear.
As in the first submission, the results of the manuscript remain based exclusively on the spatial distribution of macroseismic observations, which is described in lines 236–237 as “unevenly distributed around the epicentre, forming a trapezoidal pattern, bounded by the boundary ...”. However, the density of observations has not been analysed, although this was specifically requested. Indeed, Figures 3 and 4 show only the observation locations, many of which overlap. In addition, contrary to the authors’ statement in line 162, the population distribution does not appear to be uniform in the governmental geoportal.
The Discussion and Conclusions sections, as in the first submission, only comment on the spatial distribution of the observations — for example, “The spatial distribution of macroseismic observations proved highly informative and showed a clear correlation with major geological structures” — but do not analyse the intensity values. As already noted in the previous review, such an analysis could be useful to support the authors’ conclusions.
Technical corrections
In Figure 4, the authors have added an inset showing a small map of population density. However, the legend is not provided, and the map may be misleading because it is superimposed on topographic shading. As a result, it is not evident, for example, that the area immediately west of the TBU has zero population according to the source from which the authors obtained the data, namely https://geoportal.gov.cz/. The figure should therefore be redrawn in a clearer and more informative way.

Hide

RR by Anonymous Referee #2 (15 Jun 2026)

ED: Reconsider after major revisions (16 Jun 2026) by Simone Pilia

AR by Pavla Hrubcová on behalf of the Authors (07 Jul 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (09 Jul 2026) by Simone Pilia

RR by Anonymous Referee #1 (10 Jul 2026)

ED: Publish as is (11 Jul 2026) by Simone Pilia

ED: Publish as is (16 Jul 2026) by CharLotte Krawczyk (Executive editor)

AR by Pavla Hrubcová on behalf of the Authors (21 Jul 2026) Manuscript

Post-review adjustments

AA – Author's adjustment | EA – Editor approval

AA by Pavla Hrubcová on behalf of the Authors (05 Aug 2026) Author's adjustment Manuscript

EA: Adjustments approved (06 Aug 2026) by Simone Pilia

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2026-686', Anonymous Referee #1, 07 Apr 2026
General Comments
The paper aims to investigate deep crustal structures in the Bohemian Massif by integrating seismological data with crowdsourced macroseismic observations. While the manuscript is well-written and provides a thorough geological background of the study area, there is a significant disconnect between the stated objectives and the actual data analysis presented.
The authors claim that the study demonstrates how citizen-reported data can reveal geological controls on earthquake effects. However, the manuscript lacks the analytical support necessary to justify such conclusions. Furthermore, there is a notable absence of macroseismic literature or citations linking macroseismic intensity to geological structures, despite the extensive geological references. In its current form, the paper describes the dataset and the geological setting but falls short of providing the seismological and macroseismic analysis promised in the abstract. Major revisions are required to substantiate the interpretations with quantitative evidence.
Specific Comments
Although the abstract mentions the integration of seismological and macroseismic analyses, no actual seismological analysis is presented; the authors only provide a figure showing waveforms from some stations.

The authors state that individual responses were converted to macroseismic intensities but do not explain the methodology. It is unclear how intensities were calculated, what weights were given to specific answers, or whether intensity was assigned to individual questionnaires or geographic localities.

For low intensities (2–5) such as those discussed here, "not felt" reports are critical. The authors should clarify if they have access to these data and how they were utilized.

Figures 3a and 3c show the locations of observations but fail to display the actual intensity values. Additionally, while Figure 3d shows an area of intensity 2, there is no explanation of how this specific intensity was assigned.

In the Discussion the authors interpret the low density of observations in specific sectors (e.g., NW of the epicenter and near the RBFS structure to the east) as evidence of geological control or seismic energy attenuation. However, a low density of data points may simply reflect low population density or a lack of participation, which provides no objective evidence regarding the actual intensity value. Moreover, in Figure 4 the lack of observations NW of the epicenter appears to coincide with low-density areas. To support these claims, the authors should show the density of observations relative to the population and provide attenuation plots of the intensity values for those specific sectors.

At line 143, it is claimed that a booming sound often preceded the shaking. However, the attached questionnaire does not include a question regarding the timing of the sound; the authors must explain the source of this information. It would also be beneficial to provide a map showing the spatial distribution of these acoustic reports.

At line 247, the macroseismic fields are compared to a field with quadrupolar symmetry, but no bibliographic references are provided to support the existence of such a field.

The manuscript does not specify how the population was invited to complete the questionnaires, which is a vital part of assessing crowdsourced data quality.

Technical Corrections
The citation "Cifelli et al., 1999" (line 54) is missing from the References section.

The Appendix, which defines magnitude and macroseismic intensity, is unnecessary for a specialized scientific journal like Solid Earth and should be removed.

The authors should provide access to the dataset in a dedicated "Data Availability" section.
Citation: https://doi.org/10.5194/egusphere-2026-686-RC1
- AC1: 'Reply on RC1', Pavla Hrubcová, 17 May 2026
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-686/egusphere-2026-686-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2026-686-AC1
RC2:
'Comment on egusphere-2026-686', Anonymous Referee #2, 13 Apr 2026

The paper by Hrubcova and coauthors aims to constrain source characteristics, and deep propagation properties by using online macroseismic questionnaires collected after two recent earthquakes.

Despite the efforts are appreciable, there are many questionable points in the actual release, for which I suggest a major revision, or resubmission. They are listed below.

Major points:

1) About the Tectonic and structural context (lines 56-68, 171-202), text and figures are poorly informative of the actual expected tectonic seismicity: I suggest shrinking the description of the large scale-long time evolution of the orogenic belt in favour of a more detailed qualification of the present seismicity (actually lines 70-76): fig 1 is not sufficiently readable, consider to combine the geological panel with a physical map showing main events from CZEQ catalogue, station locations (e.g. moving the inset of Fig.2) showing for example the country's border, as common reference line.

2) About the selected earthquakes (lines 95-128), no reference is given for the solutions proposed, no details are provided about the location method, accuracy of the solutions and depth control with such a limited station coverage in the surroundings of the epicenter. Searching on ISC bullettins, the solutions provided in the manuscript nearly coincides with the ones given by national agency IPEC The Institute of Physics of the Earth; quite a lot of mining events are listed by ISC, close in space (epicenters) and time to the two mentioned tectonic events: if true, they deserve to be mentioned; a table of the identified aftershock is more informative than the actual Tab 1 (that anyway has to be mentioned in the block of focal mechanism description -lines 122-128). Consider to add a cross-correlation graph/ waveform comparison of the two events at the same station in the inset of Fig 2, to support they are co-located and with the same source mechanism. Some considerations concerning the theoretical radiation pattern of S-waves have to be added too.

3) last but the most important: I find critical and not properly presented the criteria used to assign the macroseismic degree from the questionnaires (basically described only at line 148-154). The literature in Europe on this subject is wide, but basically not quoted. Considering the formulation of questions provided in English in the Annex questionnaire, I believe the indicators of the "strength" of the shakings are still vague (for example the "observer's feelings and reactions" do not include the doubt/surprise, no fear or reaction that is usually associated with degrees II-III), and the final assignment of degrees III, IV and IV-V may overestimates the intensity. A better representation of the population density and description of the engagement of population for the compilation of questionnaires is welcome.

Minor points:

a) magnitude 3.1-3.5 cannot be defined as moderate earthquakes (usually 4.0-5.5), but light ones

b) line 54, Cifelli et al not in reference list

c) line 73 and 389 CZEQ catalogue reference lacks the date

d) references starting at lines 331, 365, 386 and 393 are not cited in the text

e) mistype at lines 407-409

f) wrong date? at reference starting at line 422, in the text quoted without a,b

Citation: https://doi.org/10.5194/egusphere-2026-686-RC2
- AC2: 'Reply on RC2', Pavla Hrubcová, 17 May 2026
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-686/egusphere-2026-686-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2026-686-AC2

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

AR by Pavla Hrubcová on behalf of the Authors (17 May 2026) Author's tracked changes Manuscript

EF by Mario Ebel (18 May 2026) Author's response

ED: Referee Nomination & Report Request started (20 May 2026) by Simone Pilia

RR by Anonymous Referee #1 (29 May 2026)

Suggestions for revision or reasons for rejection

Hide

RR by Anonymous Referee #2 (15 Jun 2026)

ED: Reconsider after major revisions (16 Jun 2026) by Simone Pilia

AR by Pavla Hrubcová on behalf of the Authors (07 Jul 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (09 Jul 2026) by Simone Pilia

RR by Anonymous Referee #1 (10 Jul 2026)

ED: Publish as is (11 Jul 2026) by Simone Pilia

ED: Publish as is (16 Jul 2026) by CharLotte Krawczyk (Executive editor)

AR by Pavla Hrubcová on behalf of the Authors (21 Jul 2026) Manuscript

Post-review adjustments

AA – Author's adjustment | EA – Editor approval

AA by Pavla Hrubcová on behalf of the Authors (05 Aug 2026) Author's adjustment Manuscript

EA: Adjustments approved (06 Aug 2026) by Simone Pilia

Journal article(s) based on this preprint

19 Aug 2026

Public response to two rare earthquakes: crowdsourcing constraints on crustal structure in south Bohemian Massif

Pavla Hrubcová, Matěj Machek, Jiří Vackář, Anna Pohořalá, Hana Kampfová Exnerová, Petr Špaček, and Jan Zedník

Solid Earth, 17, 979–989, https://doi.org/10.5194/se-17-979-2026,https://doi.org/10.5194/se-17-979-2026, 2026

Short summary

Pavla Hrubcová, Matěj Machek, Jiří Vackář, Anna Pohořalá, Hana Kampfová Exnerová, Petr Špaček, and Jan Zedník

Supplement

https://doi.org/10.5194/egusphere-2026-686-supplement

Pavla Hrubcová, Matěj Machek, Jiří Vackář, Anna Pohořalá, Hana Kampfová Exnerová, Petr Špaček, and Jan Zedník

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Two moderate earthquakes near Mirotice (Bohemian Massif) in 2024 and 2025 were analysed using seismological and crowdsourced macroseismic data. Both events occurred at unusually large depths (22–24 km) and were widely felt. Non-circular macroseismic patterns reflect tectonic control and contrasting attenuation between different tectonic units and constrain subvertical structures within the Bohemian Massif. Normal faulting matches the regional stress field, suggesting deep structural control.


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